Altered Expression of Two Small Secreted Proteins ( ssp4 and ssp6 ) Affects the Degradation of a Natural Lignocellulosic Substrate by Pleurotus ostreatus

• Published in: International journal of molecular sciences Vol. 24; no. 23; p. 16828
• Main Authors: Yarden, Oded, Zhang, Jiwei, Marcus, Dor, Changwal, Chunoti, Mabjeesh, Sameer J, Lipzen, Anna, Zhang, Yu, Savage, Emily, Ng, Vivian, Grigoriev, Igor V, Hadar, Yitzhak
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 27.11.2023; MDPI
• Subjects: BASIC BIOLOGICAL SCIENCES; Biomass; Cellulose; Enzymes; Gene expression; Genomes; Lignin; Lignocellulose; pectinase; plant biomass degradation; Proteins; small secreted protein; SSP; white rot fungus; SSP; small secreted protein; white rot fungus; lignin; pectinase; plant biomass degradation
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms242316828

is a white-rot fungus that can degrade lignin in a preferential manner using a variety of extracellular enzymes, including manganese and versatile peroxidases (encoded by the and genes, respectively). This fungus also secretes a family of structurally related small secreted proteins (SSPs) encoded by the genes. Using RNA sequencing (RNA-seq), we determined that and are the predominant members of this gene family that were expressed by during the first three weeks of growth on wheat straw. Downregulation of in a strain harboring an RNAi construct (KD ) was then confirmed, which, along with an increase in transcript levels, coincided with reduced lignin degradation and the downregulation of and . In contrast, we observed an increase in the expression of genes related to pectin and side-chain hemicellulose degradation, which was accompanied by an increase in extracellular pectin-degrading capacity. Genome-wide comparisons between the KD and the wild-type strains demonstrated that silencing conferred accumulated changes in gene expression at the advanced cultivation stages in an adaptive rather than an inductive mode of transcriptional response. Based on co-expression networking, crucial gene modules were identified and linked to the knockdown genotype at different cultivation times. Based on these data, as well as previous studies, we propose that SSPs have potential roles in modulating the lignocellulolytic and pectinolytic systems, as well as a variety of fundamental biological processes related to fungal growth and development.